Manufacture of turbine oils



Oct. 15, 1940. I LIOVELL 2,218,133

MANUFACTURE OF TURBINE OILS Filed Feb. 6, 1959 Fmdiondi'or V 78Percolahnq Fil'her Propane lnvenror: Lawrence L. Lovell Patented Oct.15, 1940 UNITED STATES PATENT orrlca MANUFACTURE OF TURBINE OILSLawrence L. Lovell, Wood River, 111., assignor to Shell DevelopmentCompany, San Francisco, Calif., a corporation of Delaware ApplicationFebruary 6, 1939, Serial No. 254,827

10 Claims.

This invention deals with a method for producing hydrocarbon oils, suchas light lubricating oils, and which are highly resistant to sludgeformation, and more particularly is concerned with the manufacture ofturbine oils by a method involving known steps and requiring nothingmore than conventional petroleum refining equipment, wherebysatisfactory turbine'oils may be produced from stocks heretoforeconsidered more m or less unsuitable for this purpose.

It is a purpose of my invention to produce a stable oils suitable asturbine oils, transformer oils, spray oils, medicinal oils, etc. It isanother purpose to produce such oils by steps requiring conventionaltreating equipment. It is another purpose to treat hydrocarbon oils withsulfuric acid and neutralize them without the use of caustic alkali or'contact clays or both; and it is a further purpose to produce acidtreated oils free from objectionable sulfuric acid reaction productswhich are frequently left in the oil by the conventional methods ofneutralization. It is well known that turbine oils must be moreresistant to sludge formation by the action I of which they come incontact during use than any other type of-lubricating oils. Sludgeinter-- duced oils with very bad emulsion properties after aging, and,in fact, itwas believed by many I that solvent extraction was moreharmful than useful in thismatter. Now,- however;I have dis.-

covered that by subjecting a solvent raiiinate of proper viscosity rangeobtained by extraction with a naphthenic solvent from aMid Continentlubricating distillate oil to a series of simple treatments, highlysatisfactory turbine oils 'can be obtained. While my method of treatingappears to be particularly useful when applied to Mid-Continentraflinates, it is, however, not limited thereto, but is applicable aswell to raflin-ates from other sources as, for example, fromPennsylvania, Gulf Coast, California, Rumania, Co-

, lombia, etc., oils.

- The solvent extraction should preferably be ing asphaltenes, resinsandthe like from the oil.

This treatment may comprise or consist of distillation, propaneprecipitation, Pilat treatment, etc. It may precede or follow, or, as.in the.

case of the Duosol process, may be carried out air and water in thepresence of the metals with.

accompanied by a treatment capable of removsimultaneously with thesolvent extraction. If necessary, the oil may also be dewaxed at onestage or another, as convenience may direct.

.The rafiinate which is substantially free from asphaltenes andpreferably free from wax, and having a preferred Saybolt Universalviscosity at 100 F. of about 100 to 200 seconds is treated at a normaltemperature, i. e., at about 50 to 140 F. with concentrated sulfuricacid.

.About 5 to 20 pounds per barrel of sulfuric acid-having a concentrationof 93% to 100%, and preferably 95% to 99%, is used advantageously. Thistreatment may be carried out in batch or continuously, and anyconventional -means for mixing, such as air blowing or-mechanicalmixing, are applicable. The oil so treated is allowed I to, settle, andinsoluble sludge is removed as completely as possible. A small amount ofwater, e. g., about /8 to 2 per cent may be added to the sour oiltohydrolize the soluble sludge and to effect precipitation of suspendedpepper'sludge. Additional sludge, which is thereby settled, is re-'moved. I

Instead of removing soluble sludge by hydrolysis with water, it maybe-extracted with suitable solvents such as methyl or ethyl alcohol,acetone, etc. In the course of this treatment, whether it be hydrolysisor extraction, the color of the oil is materially improved.

The sludge-free oil which still contains dis-. solved S02 is blown withair or other convenient gas which is substantially chemically inertunder .the conditions of this blowing, such as CO2, flue gas, nitrogen,hydrogen,etc., at an elevated tem-. perature below 200 F., e.'g.,preferably between .about 'l50l90 F. to drive off the dissolved S02.TheSOz should be removed substantially completely, and this blowingtreatment should be continued until a sampleof the oil tested shows anegative reaction for S02. S02, if allowed to remain in the oil'atthisstage, will promote side reactions. in the next following step andinduce the formation of oxidized substances, which may have adetrimental effecton the qualities of the finished turbine oil. It isfurther of importance that in the S02 removal step the temperature be 1kept below about 200 F. because at higher temperatures undesirable sidereactions may and frequently do take place.

After the last traces of son have been elimi may settle outuponstanding. The time rebe polymerization products of unstablecomponents in the oil, may vary from about one to two hours at 300 F. totwo to three days at 220* quired to form these solids, which I believeto F. At 250-270 F., normally between about 8 to hours of air blowingare required. At temperatures below 220 F., the polymerization normallyremains incomplete, no matter how long blowing is continued, and attemperatures above 300 F. undesirable oxidation reactions makethemselves felt.

Instead of air, other oxygen-containing gases, such as pure oxygen, ornon-oxidizing gases, may be used. However, if non-oxidizing gases areused, the polymerization proceeds very slowly and often remainsincomplete.

The suspended solids in the blown oil are so finely divided that theycannot be removed completely by settling. Moreover, frequently coloredsubstances are formed in the high temperature blowing which are solublein the oil and which must be removed by means other than settling. Ihave found that both the suspended and dissolved harmful impuritiescontained in the oil after this stage may be removed by simplepercolation, preferably at a temperature below about 100 F., of the oilthrough a suitable, active,

preferably naturally active, percolation clay such shown.

as Florida clay, Attapulgas clay, fullers earth, etc. operation,although coarser or finer clay may be used if desired. The oil resultingfrom the percolation has a light color and has the stability which isrequired of turbine oils. If desired, activated clays may be used,although I prefer naturally active clays.

The chemistry involved in the air blowing at the temperatures between220-ilil F. is not well understood. In particidar, it is difiieult toexplain why unextracted mineral oils such as ordinary Mid-Continentdistillates normally yield relatively dark oils of poor stability whentreated as above, and that treatment with excessive amounts of clay doesnot substantially improve their stability. Further, I have found thatelimination of all the insoluble acid sludge prior to the hightemperature air blowing at 220-300 F, as well as at least a majorportion of the soluble sludge together with dissolved S02 is essential.It is, however, relatively immaterial by what means this isaccomplished. For example, I may treat the acid treated acidic oil,which has been i'reed from insoluble sludge but which contains smallamounts of dissolved sludge, with liquid water at a temperature above212 F. and under superatmospheric pressure, if desired, in the presenceof an amount of a base such as caustic soda, lime, aqueous ammonia, etc.However, I do prefer the method hereinbefore described, of hydrolyzingwith water at normal pressure, settling additional sludge formed therebyand eliminating $02 by blowing attemperatures below 200 F. This methodis simple, eflective, inexpensive and consumes no chemicals other thanair and water.

My invention will be more fully understood from the accompanying drawingwhich represents a flow diagram of a preferred form of my process.Topped mineral crude oil containing lubricating fractions substantiallyfree from gasoil and lighter components enters extractor l near itsbottom through line 2 from a source not Propane is simultaneouslyinjected through line 3. Anaphthenic solvent, such as liquid S02,furfural, phenol, cre'sylic acid, betabeta-dichlorethyl ether, etc., isintroduced into the top of the extractor I through line 4. The propanesolution and naphthenic solvent flow countercurrently through theextractor I, extract I prefer to use a 30/60 mesh clay for this thebottom of the extractor through line 5,-and

rafiinate-propane solution flowing through line 8 to heater '1 andcolumn 8 where propane containing traces of naphthenic solvent isflashed off. Rafilnate free of solvent is conducted through heater 9 inline l0 to fractionating column II where a light lubricating distillatehaving preferably a Saybolt Universal viscosity at 100 F. of 150 to 160seconds is takenoverhead through line l2, residue being withdrawnthrough bottom line IS. The distillate vapors in line l2 are condensedin condenser l4 and condensate is stored in tank i5.

Lubricating distillate is conveyed from tank it by pump iii in line illto agitator iii, which is equipped with steam heating coil l9, sludgeline 20, air line 2i and lines 22 and 23 for introducing concentratedsulfuric acid and water, respectively. When the agitator has been filledwith rafiinate distillate oil to the desired level and the temperaturehas been adjusted to between 50 and 140 F., the proper amount ofsulfuric acid is dumped into it. Air is then admitted through line 2! toprovide the necessary agitation, and after sludge has been formed, theair current is turned off and sludge is allowed to settle and iswithdrawn through line fill. A small amount of water is now introducedinto the. oil through line .23 and is agitated with the oil to efiectremoval of the suspended pepper sludge and hydrolysis of the dissolvedsludge. The secondary sludge so formed is settled and drawn through line2b. The oil which is now substantially sludge-free but containsdissolved S02 is heated by means of 3 coil ill to a temperaturepreferably between 150 and 190 F. At this temperature, air is blownthrough the oil to remove the dissolved S02. When this has beenaccomplished, the temperature of the charge in the agitator is furtherraised .to about 250-270 while air blowing is continued for about 8-20hours. During this period, the oil turns dark purple. Without allowingcoloring material to settle, the dark oil is cooled, is withdrawn fromthe agitator through line 2d and is'conveyed by pump 25, preferably at atemperature below about 100 F. through percolation filter 26-whioh isfilled with a suitable active bleaching clay such as fullers earth. Thepercolated oil, which is very bright and of light color, goes throughline 21 to storage tank 28.

The clay, which has been spent by contact with the oil treated asdescribed, can be revivified by burning in the conventional manner.

While in the above I have described a simplifled flow diagram of myprocess, it is understood that many modifications within the scope of myinvention are possible. For example, the differout treatments carriedout in the single agitator of pumps wherever required is consideredwithin the skill of the designer for refinery requipment.

The following example further serves to illustrate my process:

A lead lined agitator was charged with 743 barrels of a lubricating oilrafllnate distillate having a Saybolt Universal viscosity at F. ofseconds, obtained from a Mid-Continent crude by extraction by the Duosolprocess.-- The charge was treated at 80 F. with 10.1 pounds per barrel98% sulfuric acid. The resulting mixture was air agitated for 50 minutesand the sludge was allowed to settle and was drawn ofi. 0.75% water wasthen added to the sour oil and the agitation was resumed for 30 minutesat 80 F. to effect hydrolysis of dissolved sludge. The hydrolyzed oilwas settled-and an asphaltic sludge was drawn 011. The oil was thenpassed through a heat exchanger into another lead lined agitator. Thetemperature of the oil after transferring was 150 F., and at thistemperature the oil was blown with air free of S02.

After the removal of the S02, the oil was circulated through the heatexchanger until the temperature reached 240 F. During the heating, asmall amount of air was blown through the oil to remove the excessmoisture and to insure mixing. When the temperature reached 240 F. theair was increased until violent agitation was attained. Thepolymerization of unstable constituents was effected by blowing for 14hours with air between the temperatures of 250 and 270 F. Thepolymerized oil was then allowed to cool and was percolated throughfullers earth at a temperature slightly below 100 F. The following datawere obtained:

Some of the more important properties of the treated oil in comparisonwith the properties of a turbine oil produced by conventional sulfuricacid treatment followed by contact neutralization with clay were asfollows:

011 properties New ttiiilrbine caiirvfiggigfial Gravity, A. I. I 31.631.2. Color- 19 Say 1 +NPA. Demulsification at 130 F 1620 1620. Emulsiontest-NaOH at 130 F 1 minute 4 minutes. Steam emulsion number 30 60. RLemulsion test Initial emulsion No emulsion 900. Emulsion after 1 hour'saging--- 1000 280. Emulsion after 6 hours aging 276 180. Originalinteriacial tension, 38.9 37.7.

dynes/eentimeter. Interracial tension after 1 hours 27.8 24.8.

flgmglntgirfacial tension after 6 hours 20.4 19.0.

a 11g. Swiss turbine oil aging test Steam jet test RL emulsion alteraging Interiacial tension after aging Sludge nig./200 m 6 Acid numberSaponiiication number I For description of the RL emulsion test, see theInstitute of Mechanical EngineerPGeneral Discussion on Lubrication andLubricants Group IV Properties and Testing," October 1937, pps.

The Swiss turbine oil test is described in Schweizerischer-Verband iiirdie Matarialpriiiung'en der Technik SVMT 17, July 12,

If desired,oxidatiori or corrosion inhibitors such as phenyl alphanaphthylamine, aromatic sulfur compounds, etc., may be added to the oilstreated by my process further to increase their resistance against thesludge inducing influence of metals.

I claim as my invention:

1. In the process of producing stable hydrocarbon oils suitable forlubrication, the steps comprising treating a lubricating rafllnateobtained by extracting a hydrocarbon oil with a naphthenic solvent whichis substantially free of asphalt and resins with an amount ofconcentrated sulfuric acid suflicient to produce sludge and S02,separating the sludge-to produce a substantially sludge-free oilcontaining S02, blowing the resulting sour oil with a gas which issubstantially chemically inert under the conditions of the blowing toremove further blowing the resulting S02-free oil with an oxygencontaining gas at a temperature between 220 and. -800-? F. for a timesuflicient only to substantialiy effect polymerization of unstablecomponents of the lubricating oil, whereby the color of the oil ismaterially darkened, and contacting the darkened oil with an activebleaching clay to decolorize the oil.

2. 1n the process of producing turbine oils, the steps comprisingtreating a lubricating rafiinate obtained by extracting a hydrocarbonoil with a naphthenic solvent which is substantially free of asphalt andresins and has a. viscosity suitable for turbine oils with an amount ofconcentrated sulfuric acid suificient to produce sludge and S02,separating the sludge to produce a substantially sludge-free 011containing S02, blowing the resulting sour oil with a gas which issubstan-' tially chemically inert under the conditions of the blowing toremove S02, further blowing the resulting SOs-free oil with an oxygencontaining gas at a. temperature between 220 and 300 F. for a timesuflicient only to substantially effect polymerization of unstablecomponents of the lubricating oil, whereby the color of the oil ismaterially darkened, and contacting the darkened oil with an activebleaching clay to decolorize the oil, i

3. The process of claim 1 in which the oil is a distillate oil.

4. The process of claim 2 in which the oil has a Saybolt Universalviscosity at 100 F. of 100-200 seconds.

5. In the process of producing a turbine oil, thesteps comprisingtreating a lubricating raffinate .distillate obtained by extracting ahydrocarbon oil with a naphthenic solvent having a viscosity suitableforturbine oils with 5 to 20 pounds concentrated sulfuric acid at atemperature between 50-140 F., thereby producing soluble and insolublesludge and S02, separating the insoluble sludge, treating the resultingsour 011 containing dissolved sludge and S0: with a small amount ofliquid water to hydrolyze soluble sludge, thereby precipitating same,separating the hydrolyzed sludge, blowing the sludge-free oil containingdissolved S02 with air at a temperature below 200 F. to remove S02,further blowingthe SOs-free oil with air at a temperature between220-300 F. for a time only suflicient to substantially polymerizeunstable components of the oil whereby the color of the oil is darkened,and contacting the darkened oil with an active clay at a temperaturebelow 100 F.

6. The process of claim 5 inwhich the sulfuric acid has a concentrationof -100%,

7. The process of claim 5 in which the amount of water is to 2% of theoil.

